Automatic filling and weighing device



July 29, 1952 I R 5 BROWN 2,605,075

AUTOMATIC FILLING AND WEIGHING DEVICE Original Filed Dec. 14, 1948 s Sheets- Sheet 1 INVENTOR.

ROBERT 5. BROWN ATTORNEY R. B. BROWN AUTOMATIC FILLING AND WEIGHING DEVICE Original Filed Dec. 14, 1948 3 Sheets-Sheet 2 35 26 60 IV 20 I 'IWENTOR E T E. snow/v sy ATTORNEY y 1952 R. B. BROWN 2,605,075

AUTOMATIC FILLING AND WEIGHING DEVICE Original Filed Dec. 14, 1948 3 Sheets-Sheet 3 IZZ' UIZ- 1mm; EMUFFMI INVENTOR.

ROBERT 8. BROWN My 120 y ATTORNEY Patenteci july 29, 1952 FUNI'TED PATENT AUTOMATIC FIIi I ESiND WEIGHING Q RobeiftiB. Brown, San Francisco, Calif assign'o'r to T. RiMaiites, San Francisco, Calif.

rigiiial a pplication December ll, 1948,Serial N 0. 155,251. Divided'and this application January 1 6, 1950, Serial=No.144,872

8Cl'ai'ins.

This invention relates to -an improved automaticfilling'and weighingdevice. 'Ihis application is-a division Of applicatiOn-SeriaI Number 65,251, filed December 14,1 948. H An importantaccomplishment-cf this invention -is that it makesv possible safe use of automa-t'icmeasuring equipment with explosive materials. -Aut0matic measurement of gasoline, for example, is extremely-dangerous when electrical control devices are used, because a singlespark may .lead *to the destruction-of an entire iactory. The cost of making electrical controls explosion proof is far wgreaterthan the-entire cost of'a complete-system employing this present invention. This invention solves the problem of safe automatic measurement of explosive materials since it doesnot -use electricity'anywhere in the syste'zm, but instead'provides a sensitive,

accurate air pressure 'for control for the filling valves.

The'valve of this invention isalso capable-of use 'with non explosive materials, especially where air-operated valv'es are "used. Prior air valve c'ontrols "have eitherlacked the requisite sensitivity or have been'unable to handle a-l-arge enough-air: current by themselves and have had to be :supplemented by relays and additional valves. I The air control valve of "this invention has both i great =*sensitivity and a capacity for handling large air currents with no supplemem tal'valves or relays needed.

-A furtherproblem in-th .pasthas been that of achieving an automatic, positive, and permanent cutoii. In-air-control valves heretofore available 1 there has been the danger that if the air current supplying the control valve were cut off, the feed valve'would continue to deliver matcrial, orit might start in again accidentally. This was not only wasteful and untidy, it was extremely dangerous when explosive material would splash out over the top of a full-container. With this invention the feed valve is cutofi when the desired-quantity has-been'measured; and the'control valve is locked-so that the feed valvecannot open again until the filled container is removed from the scale-and anempty one put in place of; it. n k I One object of [the invention 1 is to. provide an improved-automatic measuring device.

eno'ther object of the invention is to provide an improved mechanism for varying the response characteristics of an automatic measuring device.

Other objects and advantages of the invention "will appear from the-followingdescription. In

accordance with US. Revised Statutes, Section 4888, specific devices are describe'clin-dtailflbiit it is not intended that the invention be thereby limited except as required by the appended claims.

In the drawings:

"Fig. -l-is a view 'inelevation and partly-in section of an automatic filling and weighing device embodying the principles of thisinvention;

Fig-21s a view in perspective, looking lfrom above, of an air-control valve which maybe employed ;in this invention;

Fig. 3 is a view in perspective,iodkingffrdm below, of the valve :shown-in FigJ2; 1

Fig.4 is a view in section taken along the plane 4--4 Fig. -2, with=the valve being shown inits latched'or ;on position; n

'Fig. 5 is a view similar to '4, wi ththe valve inits unlatched: or off position;

-'-Eig. 6 a view in section taken along thelline ii fiin Figs. 4'and 8;

-Fig. 7; is-a view in section taken alongthe line 'l'lin Fig.-4;

--Fig.-8- is a view similar to Fig. -7 with-the valve shown in-its --unlatched-or' oifv position.

Fig. -9 is aview similar -to Fig. 4-showing-a modified form of latching device.

li'ig. -10 is a view -s imilar to Fig. 4-showing a modified -f0rm-0flatch and latch release;

:Fig. 11 is-a viewsimilar to Fig. -10 with the valve shownin its unlatched or ofi --position;

Fig l-ii -is a-rear view in elevation and -partly in sectioncf --a control box for .an automatic measuring device, 1 comprising .two air control valves and a reset mechanism therefor, the adjusting mechanism on the front .of thebox being shown in dotted lines; and

-Fig."l"3 is a view in section of thereset valve shown in Fig, 12.

" This invention uses an air-operated control "'valve' inconne'ctionwith an automatic measuring system using air-controlled iee'dvalves.

The preferred control valve (claimed Iin -my December"14,- 1948) 'inc1udes'a sliding spoolvalve in; a passageway which'is 'j'oindi'by anirilt. conduit, "an outlet work conduit,andanlexhaustbr bleed conduit. A latch .me chanism normally 'holds the-valve 'in op'en position, so that air may "won; conduit is'ble'dpii through theexha'ust conduit. The control valve also includes means to reset the valve to its latched position.

The particular forms of valve illustrated in the drawings will now be discussed. Figs. 2 through 8 show a preferred form of air control valve l3. Its housing Il may be bossed, bored, and grooved to provide the conduits and to accommodate the moving parts. A valve passageway I2 extends from one end of the housing I to the other. At one end of the passageway |2 is a hollow fitting H, to which the reset air conduit may be connected. (See Fig. 12). In the other end of the passageway I2 is threaded an exhaust fitting having an opening I8 therethrough. (See Figs. 2 and 7).

Adjacent the exhaust fitting II and on both sides of the passageway I2 are two ports (see Figs. 6, 7 and 8) which lead to the outlet work conduit 2|. The twin ports 2|! are preferable because they assure better balance and quicker action than a single large port, but a single port will also give satisfactory results.

A single inlet port 22 joins the passageway I2 at a point further in from the fitting than the outlet ports 20. In the inlet conduit 23 is a fitting 24 to which may be secured the outside air inlet tube 25. (See Fig. 12) A similar fitting 26 may be threaded into the outlet conduit 2| and to the fitting 26 the outside air outlet tube 2! may be secured. When the valve III is in its on position (Fig. 4) the tube 21 carries a stream of compressed air to the controlled valve, which may be the feed valve 62 in Fig. 1.

Inside the passageway I2 is a slidable valve stem 30 comprising two spools 32 and 34 between three pistons 3|, 33 and 35. The spools 32 and 34 will pass air, but no substantial amount of air can leak past the pistons 3|, 33 and 35. The end piston 3| faces the fitting ll. Adjacent it is the spool 32 which passes air between the inlet port 22 and outlet ports 20 when the valve is in its on position (see Figs. 4 and 7). The other end of the spool is closed by the central piston 33. A second, latch-engaging spool 34 is adjacent the piston 33 and at the far end of the stem 3|! is the reset piston 35. Preferably the shoulders 36 of the spools are sloped.

' The valve 30 is urged toward the reset conduit |4 by a spring 38, which is compressed between the piston 3| and the exhaust fitting H. In this ofi position (see Figs. 5 and 7) the piston 3| blocks off the inlet port 22 from the outlet ports 20. At the same time the outlet conduit 2| is bled off to the atmosphere through the opening IS in the exhaust fitting.

In its on position (shown in Fig. 4) the valve stem 30 is held by a latch in a position where the piston 3| blocks 01f the outlet ports 20 from the bleed opening I8, and air may pass freely from the inlet port 22 through the clearance around the spool 32 and into the outlet ports 20.

A preferred form of latch 40 (shown in Figs. 4 and 5) comprises a pivoted rigid latch member having a tapered depending foot 4|. The foot 4| is adapted to engage the shoulder 36 on the spool- 34-side of the piston 33 and thereby hold the valve 30 in open position.

The housing II is bored horizontally at 42 to receive the latch pivot pin 43, and is grooved vertically at 44 so that the latch member 4|] may swing vertically about the pin 43. The foot 4| fits in a vertical bore 45 which intersects the passageway |2 at an appropriate location.

The housing II is also bored vertically at 46 to accommodate a spring 41, which is compressed between the upper surface of the latch 4|] and an Allen screw 48. The spring 4'! urges the latch member 40 down toward its latched position, but it is a weaker spring than the spring 38. The latch 43 is latched either by a mechanical device to push the piston 35 over or by the air-reset mechanism described later on in this specification.

When the reset mechanism is retracted or the reset air stream is turned off, the latch member 40 would not hold were it not for a latch release member 50, whose generally-vertically-depending foot or leg 5| rests on a step 52 in the latch 40, just above the foot 4|. The latch release member 50 is an L shaped member supported by a pivot pin 53 for swinging movement in the groove 44.

The pivot pin 53 is located vertically above the edge or" the step 52, so that the vertical component of the thrust from the spring 38 is resolved along the rigid leg 5|, and the latch 40 cannot be released until an outside force lifts the long release finger 55. Then the member 50 pivots around the pin 53, the leg 5| falls off the step 52, and the spring 38 snaps the latch 40 up as the valve 33 moves to its off position.

Preferably the latch edge below the step 52 is sloped at 56, so that during resetting the leg 5| may slide up the slope 56 until it reaches its latching position on top of the step. This structure has advantages over a straight edge, because the inclined slope gives a smooth action whereas with a straight edge, the leg 5| is latched with a sudden jerk. If the member 50 does jerk suddenly, it may bounce out of position instead of remaining on the step. Since the reset operation is usually accomplished by a single blast of air, the valve 33 might then return to its off position before the latch is secure.

For convenience, the operation of the valve I0 will be described, beginning with the valve in its oiI position (Fig. 5). The valve is first set, as described above, either mechanically or hydraulically by pressure introduced through the fitting I4 against the piston 35. The stem 30 is moved in the passageway |2 until the latch foot 4| drops down onto the spool 34 against the piston 33. At the same time the foot or leg 5| rests on the step 52 and the latch 40 holds the stem 30 in its open position. Then air passes from the inlet conduit 23 around the spool 32 and into the outlet work conduit 2|.

Air continues to fiow until the finger 55 is lifted. Then the latch release leg 5| slides off the step 52, and the spring 38 forces the latch 43 out of the notch 34. This releases the stem 30, which then moves to its off position. Then the inlet conduit 23 is blocked off by the piston 3|, and air bleeds ofi from the outlet conduit 2| through the ports 23 and the exhaust fitting IT. The latch release leg 5| rests against the shoulder 56 of the latch 40, and the stem 30 cannot be reset until forcibly moved over against the resistance of the spring 38.

Fig. 9 shows a modified latch I40 which is similar to the latch 40, except that it has no integral foot 4|. A ball |4| fits in the bore 45 below the latch M3. In latched position the ball I 4| lies on the spool 34 and against the shoulder 36 of the piston 33. The latch I40 operates very much like the latch 43, and illustrates the fact that there are equivalents to several parts of this control valve.

Figs. 10 and 11 show a modified form of latch release. The latch I45 is similar to the latch 40, except that instead of a step 52 and a slope 56,

it has a long continuous'slope I46. It is urged to a down (latching) position by a spring I41.

An' intermediate latch I50 is pivoted on a pin II directly above the vertical bore 45. The end I53 of its depending foot or leg I52 is preferably sloped, to slide on the slope I46. The latch I5!) is urged downwardly by the compression force of a small spring I51, and its horizontal arm I54 is preferably stepped at I55. The forward edge I56 of the arm I54 is also sloped. Both the step I55 and edge I56 function like their counterparts in the device shown in Fig. 4.

The depending foot or leg I8I of the release finger member I68 rests on the step I55 when in latched position. The pivot pin I62 of the member I60 is vertically above the edge of the step I55, so that the upward thrust is resolved along the rigid leg I 6I The release finger I65 operates in a manner similar to the finger 55, but has the advantage that is is even more sensitive than the single release mechanism. This type of latch and latch release thus has special suitability for exactlyweighing very small quantities. Other things being equal, a smaller force is required to lift the finger I65 than is required to lift the finger 55 in the device of Fig. 4. When the finger I65 is released, the vertical component of the thrust of the spring 38 is more than sufficient to lift the latch I45 against the two springs I41 and I51.

Fig. 1 shows an automatic weighing mechanism employing two valves of the type described and numbered Illa and b in Fig. 12. The container 60 to be filled rests on the weighing platform 6I directly beneath a dump valve 62. The conduit 58 leads from the fluid storage to the dump valve 62 through a preliminary two-position valve 59. A rod 63, lever 64 and rod 65 connect the platformGI to the scale tare beam 66 at a point adjacent but on one side of the fulcrum 61. I I

On the opposite side of the fulcrum 61 is a counterweight '68 which may be adjusted along the beam for varying the weight of material to be dispensed into the container 68.

On the same side of the tare beam 66 as the rod 65 there is a stud '69 in contact with both leaves of a double-leaf flex 10. The flex I0 prevents the scale tare beam from swinging up suddenly when the scale comes into balance. From the time the scale tare beam contacts the flex until the weighing is completed, the strength of the flex is a factor in determining its weight. There may also be another stud TI on the end of the scale beam 66, which is secured to or engages a rod I2. The rod 12 is connected to a dashpot I3 which damps the swing of the beam after the critical balance weight has been reached. These are usual scale parts and individually constitute no part of the present invention.

Secured to the same side of the tare beam 86 as the counterweight 68 is a control rod I5 which extends up into a control box 16. This box is (the back side of which is shown in more detail in Fig. 12) holds the two control valves Ina and I'Ilb. These valves are identical and are the same as the valve I0 which has been described above in detail. Both of their housings II are preferably bored horizontally at 11, in line with the axis of cam 8| is rotated on its shaft 82, its associated valve housing II is moved around its pivotal mounting I8 and the vertical elevation of the outer end of the finger 55 is changed.

Each cam 8I may be adjusted from outside the box 16 by a device similar to that described in copending application, Serial No. 681,660, filed July 6, 1946 which has been abandoned. It comprises a lever arm 83 (see Fig. 1 an the dotted lines in Fig. 12) rigidly secured to the cam shaft 82 and split at its outer end 84 to provide a fork to embrace the curved, threaded rod 86. The fork 84 also engages a wheel 85 mounted on the threaded rod 86 so that movement of the wheel 85 moves the arm 83 and determines the rotational position of the cam shaft 82 and the cam 8I. A look nut 81 is threaded around the rod 86 and serves two functions: to hold the wheel 85 from accidental displacement and to cooperate with the wheel during setting, to give a comparison of how much motion has been or is to be given the cam shaft.

When the wheel 85 moves along the rod 86, it turns the cam shaft 82 and the cam 8I. As the cam 8I revolves it lifts or lowers its associated valve housing II, with the result that the finger 55 is moved up or down, changing the point at which it will be engaged when the scale is weigh- In weighing, end finger 55 is actuated by an adjustable collar 90, 9| secured to the rod I5. When the scale beam 66 is moved, the rod I5 is pushed upwardly. At a predetermined weight the lower collar 90 will engage the finger 55 of the lower valve Illa, tripping its latch 48 and cutting off the air through its outlet tube 21. This moves the valve 59 to its dribble position. As the weighing continues, when the exact weight is reached, the collar QI engages the finger 55 on the upper valve Iflb and cuts off its outlet air supply through its outlet tube 21. This closes the dump valve 62.

There are thus several adjustments affecting the points at which the valves Illa and Nib will close; the counterweight 68, the flex T0, the position of the adjustable collars 90 and 9| and the position of the cams 8|. In setting up to weigh out material, the first rough adjustment is made with the counterweight 68. The differences between cutofi points in the two valves is determined by the flex III andby the collars 90 and SI. The flex Hi is normally standardized, and the collars are adjusted for a given type of operation. Then the fine adjustment is obtained by the knurled wheel 85.

A great advantage is obtained by using the present invention with-a visual indicator 95. The needle 96 is adapted to rest at the center of the dial face 9'! when the scale is in perfect balance. If the collars 90 and 9| (especially the latter) have not been adjusted perfectly, the indicator will indicate this error, for, if the scale is not in perfect balance, the needle 96 will be to one side or the other of the center mark. If the filled container 60 is underweight, the wheel 85 is moved to raise the finger 55 somewhat on the valve Illb, so as to delay its closing of the dump valve 62. If the indicator shows that the container is overweight, the direction of the wheel 85 is reversed to correct for the next container. The weight can be made as exact as the indicator will read.

The valve 62 has two rates of flow and 'a closed position. Air pressure'through the tube I00 (Fig. 12') moves both valves Illa and III!) to their "on position, which in turn opens the dump valve 62 and the dribble valve 59 to its maximum feed position. When the'valve I-(Ia is tripped by the 7 collar 90, it closes off the air through the tube 98, bleeds ofi the pressure through the exhaust opening I8 and the valve 59 moves to its dribble or minimum open position. When the second valve IOb closes oil the air through the tube 99, the dump valve 62 is snapped completely shut, and will remain so until the valves Ifla and [b are reopened.

The valves Illa and let, as stated above, must be positively reset. In the device shown in Figs. 1 and 12, an air-reset mechanism is shown.

All of the air (both for resetting and for actuating the valves 59 and 62) may come from a single air supply conduit I09 connected to a suitable compressor (not shown). The air passes through a suitable moisture filter I DI and a lubricator I52 (see Fig. 1) into a manifold I03 inside the box l6. (See Fig. 12.) The manifold I03 has three outlet openings I85, I96 and I 01. The flexible pipe 250. leads from the outlet I05 to the inlet fitting 24 of the lower control valve Ita; a flexible pipe 255 leads from the outlet I06 to the inlet fitting 24 of the upper control valve I017. The third outlet I0: supplies air to a reset valve I it} through a pipe I I I.

The reset valve I I5 is shown in section in Fig. 13. Its housing H2 is bored through to provide a central passageway I I3 having a narrow central portion I I4 and wider outer portions or chambers H5 and H6. A hollow plug II! is threaded into the end H5.

An inlet conduit 12!) leads to the narrow passageway portion H11, and two outlets I2I and I22 lead from the chamber I I5 to the flexible air reset tubes I5a and I5b, respectively, of the valves IM and Nb.

A valve stem I25 is slidable along the passageway II3. Secured to the front end of the stem I25 is a closure member I26, whose rear edge I21 normally rests against the seat I28 and closes oif the passage II4 from the chamber II5. front end I29 of the member I26 is adapted to close the opening I30 of the plug, and when seated serves to send all of the air pressure from the inlet I29 out through the outlets I2! and I22. When the member I26 is in between its two seating positions, however, the air bleeds out the opening I30, so that the valves Ida and I010 cannot be reset unless the stem I25 is pushed all the way in. This prevents unintentional resetting when the cap I33 is touched accidentally.

The opposite end of the stem I25 extends out through packing I3I and a packing nut I32, which prevent leaks from the chamber I I6. The stem I25 extends outside the housing H2, and at its end a reset cap I33 is rigidly held by a set screw I34. A spring I35 between the cap I33 and housing I I 2 normally urges the cap I33 away from the housing and keeps the inner end I27 of the closure member I26 against its seat I28. For convenience, the cover of the box I6 is bored, and the cap I 33 extends outside the box on its front side (see Fig. 1).

When the cap I33 is depressed, the stem I25 is moved in against the force of the spring I35. At first, some of the air leaks out through the opening I30, but when the end I28 of the closure member I26 rests against the opening I30, the reset lines I5a and I5?) are filled with air, and the valves I00. and IOb are simultaneously reset in the manner already described.

After each container 66 is filled, it is replaced with another empty container 60. Then the button I33 is pressed by the operator. The valves Illa. and IOb open, and they, in turn, open the dump valve 62 and the dribble valve 59. Feeding The 8 begins fast and is automatically cut down to a dribble. When the exact weight is reached, the valve 62 is automatically cut off. Then, the filled container is again replaced with an empty container, and the cycle is repeated.

It will be evident from the above description and operation that the valve operates entirely on air pressure and requires no electrical mechanism. When the finger 55 is lifted the valve is positively tripped and must then be reset positively.

It will be noted that the large stream of air which can be transmitted directly through each valve I0 obviates the need for a supplemental valve. At the same time, the valve is very sensitive and responds quickly to the releasing of the latch. It bleeds off the air in the work outlet conduit 2I so that the dump valve 62 is closed immediately.

I claim:

1. An automatic filling and weighing system employing air-controlled feed valves, comprising a scale having a tare beam; a feed valve for delivering material into a container on said scale, said feed valve being actuable by air pressure to initiate the filling of said container; and a control valve for turning on and off the air to said feed valve, said valve including a slidable closure member, means urging said closure member to a normally closed position, means to move said slidable member to an open position for turning on said feed valve, latch means to hold said slidable closure member in said open position, said latch means being urged toward a position away from its holding position by said slidable member urging means, and a pivoted latch release member having a rigid, generally vertical, depending foot adapted to hold said latch means in locked position against the force of said urging means, and also having a rigid arm, rigidly connected with said foot and extending generally horizontally into a position where it can be engaged and lifted by the swing of said tare beam to enable closure of said valve when a predetermined weight is reached.

2. In an automatic filling and weighing system, having a balance with a tare beam and a flex to restrain the swing of said tare beam; means for feeding material into a container being weighed, said feed means having a valve with two rates of feed and a dump valve, said valves being controlled hydraulically to open them for a fast feeding position, a slow feeding position, and a closed position; the combination of a control means for turning on and off the hydraulic fluid to said feed means, said control means including two valves, each having a closure member, means for urging said closure member to a normally closed position; means for moving said closure member to an open position, latch means for holding said closure member in said open position, said latch means being urged toward a direction away from its holding position by said closure member urging means, and a pivoted latch release member having a rigid generallyvertically-depending foot adapted to hold said latch means in locked position against the force of said urging means, and also having a rigid arm, rigidly connected with said foot and extendng generally horizontally into a position where it can be engaged and lifted by the swing of said tare beam to enable closure of each said valve when a predetermined weight is reached.

3. An automatic filling and weighing system. including in combination, a balance having a tare beam and a flex to restrain the swing of said tare beam; means for feeding material into a container being weighed, said feed means having two rates of feed and being controlled pneumatically for actuation between a fast-feeding position, a slow feeding position, and an off position; a control means for turning on and off the air to said feed means, said control means including two valves, each having a closure member, spring means urging said closure member to a normally closed position, setting means for moving said closure member to an open position and turning on its associated feed means, pivoted latch means for holding said closure member in said open position, said latch means being urged toward a rotational position away from its holding position by the force of said spring means and a pivoted latch release member having a rigid generally vertically depending foot adapted to engage said latch means and hold it in locked position against the force of said spring means, and also having a rigid arm rigidly connected with said foot and extending generally horizontally out from the pivot point; a rod secured to said tare beam and adapted to move as said beam swings; and means on said rod for engaging and lifting said rigid arm of the latch release member of each control means so as to cut off the air first to one said feed. means and then the other as the tare beam moves.

4. In an automatic filling and weighing system for liquids employing an air-controlled feed valve, and having a balance having a tare beam, at counterweight on said tare beam and a flex to restrain the swing of said tare beam, and a feed valve for delivering liquid into a container being weighed, said valve being normally closed and opened by air pressure; the combination of a control valve for turning on and off the air to said feed valves, said valve having a closure member, a spring urging said closure member to a normally closed position, means for moving said member to an open position for passing air to its feed valve, pivoted latch means for holding said closure member in said open position, said latch means being urged toward a direction away from holding position by the action of said spring and a pivoted latch release member having a rigid, generally vertically depending foot acting to hold said latch means in locked position against the urging force of said sprng, and also having a rigid arm rigidly connected with said foot, and extending generally horizontally out from the pivot point of said release member; a rod secured to said tare beam and adapted to move as said beam swings; and collars secured to said rod for engaging and lifting said rigid arm of said latch release member so as to swing said foot off said latch means and release said closure member, whereby it moves under the pressure of said spring to its closed position.

5. The system of claim 4 including a control box; a housing for said control valve pivotally supported in said box for swinging movement about a point distant from its latch release member; said housing also having a pair of guide members adjacent said latch release member; and cam means fitting between and in contact with said guide members for swinging said housing about its pivot and thereby changing the actuation position of said latch release means.

6. The system of claim 5 including a control box; a housing for said control valve pivotally supported in said box for swinging movement about a point in line with the horizontal axis of said latch release member; guide means secured to said housing adjacent the end where said latch release member projects; and cam means engaging said guide means for positively controlling the position of said housing and thereby the actuation position of said latch release memher.

7. The system claimed in claim 6 in which said guide means comprises a pair of spaced-apart arms projecting from said housing and said cam means includes a shaft journaled in said box and a disc eccentrically mounted on said shaft and filling the space between said arms so that said disc is always in contact with both of said arms.

:8. The system claimed in claim '7 in which there is a curved threaded rod secured to the outside of said box on an arc circumferentially around said shaft, an arm rigidly secured to said shaft outside said box, and a wheel member rotatably supported on the end of said arm and engaging the threads of said threaded rod, said wheel controlling the position of said cam and thereby said latch release member by its position along the threaded rod.

ROBERT B. BROWN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 616,862 Richards Dec. 2'7, 1898 826,502 Hanson July 17, 1906 2,264,562 Bryant et al Dec. 2, 1941 2,278,655 James Apr. 7, 1942 2,317,639 Ray Apr. 27, 1943 2,398,887 Drinnon Apr. 23, 1946 

